1. Field of the Invention
The present invention is directed to a method and a device for determining, i.e., detecting, wear in a holding brake which is used for braking a shaft driven by a motor.
2. Description of the Related Art
As a rule, a holding brake comprises an electromagnet which holds a shaft at a standstill via brake disks. That is, the holding brake reliably prevents the rotation of the shaft. For reasons of operating safety, it is imperative that a holding brake of this type brakes with sufficient strength. The braking action may be affected by wear and/or by the development of a layer of corrosion on brake disks when the brakes have not been actuated for a long period or have been stopped for a long time. For safe and reliable operation of the shaft on which the holding brake is arranged, reliable detection of wear is essential.
The object of the present invention is to detect wear in a holding brake in the most efficient manner possible and with sufficient dependability.
The object is met by a process for determining wear of a holding brake via an electronically controlled brake test, the holding brake comprising a brake arranged for braking a shaft drivable by a motor. The process comprises the steps of presetting a reference angular position which is to be traveled by the motor during the brake test and which deviates from a current actual angular position and presetting a maximum torque to be applied by the motor to the shaft when traveling to the reference angular position during the brake test, applying a torque not greater than the maximum torque for rotating the motor and the shaft to the reference angular position while the holding brake is applied, and determining the existence of wear when the shaft rotates, i.e., when the torque of the motor exceeds the holding power of the holding brake.
The object is also met by a device for determining wear in a holding brake via an electronically controlled brake test, the holding brake operatively arranged for braking a shaft which is drivable by a motor. The device includes a reference value preset device for presetting a reference angular position which is to be traveled by the motor during the brake test and which differs from a current actual angular position of the motor. The reference value preset device also presets a maximum limit torque to be applied by the motor during the brake test. The device further includes a detection device for detecting whether the shaft rotates during the brake test, wherein the existence of wear is determined when the shaft rotates and the absence of wear is determined when the shaft does not rotate
The present invention allows the detection of wear in a very dependable manner by presetting a reference angular position of the shaft and a limit torque for a motor which is connected for driving the shaft. The present invention detects whether the shaft rotates when the holding brake is on and the motor applies the limit torque to the shaft.
This can be realized in an especially efficient manner particularly in a construction with a stored program control which presets a limit torque and reference angular position for the motor and reads out the actual angular position of the motor to determine whether the shaft which is drivable by the motor rotates. Rotation of the shaft indicates wear is present in the holding brake for the shaft.
A solution to this problem that is familiar to the person skilled in the art includes monitoring the current and voltage at the holding brake. However, this method does not carry out a sufficiently dependable monitoring of wear in a holding brake caused by the development of layers of corrosion on brake linings of the brake.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.